JPH0624150Y2 - Spark plug with temperature and pressure sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention relates to a spark plug with a temperature and pressure sensor used in a compatibility test between a spark plug and an engine.

[Prior Art] In order to determine the optimum spark plug model for engine ignition, various spark plugs with different specifications are attached to the engine, the engine is operated, and the mixture ratio, cylinder temperature, intake air temperature, ignition timing, rotation Change the number, intake pressure, exhaust pressure, etc. and perform a compatibility test between the spark plug and the engine. During this so-called matching test, it is necessary to measure the temperature of the tip of the center electrode of the spark plug and to know whether the tip of the center electrode is at an appropriate temperature or whether it is overheated or overheated. It is important in making a decision. The reason for measuring the temperature is that if the temperature of the center electrode is too low, carbon deposits accumulate and the ignition performance deteriorates, and if the temperature is too high, preignition occurs before normal spark ignition.

There has been proposed a spark plug capable of measuring the temperature of the tip portion of the center electrode during operation of the engine during the above-described matching test of the spark plug and the engine.
As an example, FIG. 4 shows a spark plug B with a temperature sensor. The spark plug B with a temperature sensor has an axial hole 31 extending from the rear part to the vicinity of the tip in the center electrode 3, and a temperature sensor for measuring the temperature of the tip of the center electrode 3 is formed near the tip of the hole 31. A thermocouple 5 is incorporated. The tip of the thermocouple 5 is a temperature measuring contact 51, which is a connection point of the chromel wire 52 and the alumel wire 53 forming the pair of the thermocouple 5. Since this spark plug B has a configuration in which a change in the outer structure of the measuring portion (ignition portion) is minimized as compared with the original spark plug, it is possible to determine the combustion state during the matching test between the spark plug and the engine. The temperature of the spark plug (the tip of the center electrode), which is one of the parameters that governs, can be accurately measured, which is convenient for grasping the combustion state such as the occurrence of preignition.

[Problems to be solved by the invention] In recent years, however, the use conditions of spark plugs have become stricter as engine output has increased. When measuring the temperature of the tip of the center electrode in this matching test, the temperature may rise due to abnormal combustion. At this time, it is impossible to determine whether the abnormal combustion is due to engine knocking, pre-ignition of the plug, or post-ignition. Therefore, the cause of the temperature rise is unknown, and an error occurs in the determination of the compatibility of the spark plug and the engine.

The object of the present invention is to provide both a temperature sensor and a pressure sensor at the tip of the center electrode to minimize changes in the external structure as compared with the original spark plug, and to perform knocking detection and temperature measurement at the same time. Thus, it is possible to provide a spark plug with a temperature and pressure sensor that can accurately determine the cause of the temperature rise at the tip of the center electrode during the matching test.

[Means for Solving the Problems] In order to achieve the above object, in a spark plug with a temperature and pressure sensor of the present invention, a tubular metal shell is fitted with an insulator with a shaft hole, and a center electrode is inserted into the shaft hole. In the spark plug, a hole is formed in the center electrode in the axial direction from the rear part to the vicinity of the tip, a thermocouple is incorporated in the vicinity of the tip of the hole, and a temperature sensor for measuring the temperature of the tip of the center electrode is formed. A structure is adopted in which an annular pressure sensor is arranged on the engine mounting seat surface of the metal shell. More preferably, a configuration is provided in which a coaxial three-pole connecting terminal including a high-voltage contactor and a pair of thermocouple contacts is provided at the rear end of the center electrode.

[Operation and Effect of Invention] The spark plug with the temperature and pressure sensor of the present invention is
The temperature sensor provided at the tip of the center electrode and the annular pressure sensor provided on the engine mounting seat surface of the tubular metal shell provide two sensors. [Operation 1] Despite having two sensors No
Compared to the original spark plug, there is very little change in external structure.

[Effect 1] In the compatibility test between the spark plug and the engine, when the spark plug is attached to and detached from the engine, it is easy to handle.

[Operation 2] In the compatibility test between the spark plug and the engine, at the time of measuring the temperature of the tip portion of the center electrode of the spark plug (hereinafter referred to as the spark plug temperature), at the same time as knocking and the cylinder (engine combustion chamber) pressure peak position, Can be detected.

[Effect 2] By the above operation, (a) the spark plug temperature is normally stable in a steady operation state, but the temperature may rise due to abnormal combustion. In such a case, at least the knocking, which is one of the causes of abnormal combustion, can be clearly detected by simultaneously observing the in-cylinder pressure, which is effective in analyzing the combustion state of the engine under these operating conditions.

(B) In a compatibility test between the spark plug and the engine, knocking may occur even when the spark plug temperature is stable, and the engine may be damaged. Knocking in this case is difficult to determine by the measurement by the sensitive method, especially under a high rotation operating condition. On the other hand, as in the present invention, the structure in which the annular pressure sensor is arranged on the engine mounting seat surface of the metal shell allows the knocking to be clearly detected, and has the effect of preventing engine damage.

(C) When developing an engine, it is important to investigate the combustion state. The spark plug temperature measurement, knocking, and cylinder pressure peak position of the parameters that govern the combustion state can be measured at the same time without extra machining of the engine, which is convenient for grasping the combustion state.

In addition, the rear end portion of the center electrode is provided with a coaxial three-pole connecting terminal including a high-voltage contactor and a pair of contactors for a thermocouple. [Action 3] Two sensors are provided. in spite of,
The terminal part becomes compact.

[Effect 3] In the compatibility test between the spark plug and the engine, when the spark plug is attached to and detached from the engine and the shield cap is connected to the plug connection terminal, the workability is good and the handling is easy.

[Embodiment] The present invention will be described based on an embodiment shown in Figs.

The spark plug A with a temperature and pressure sensor has a tubular metal shell 1 for mounting in a combustion chamber of an engine.
The cylindrical metal shell 1 has a ceramic insulator 2 with a shaft hole.
Is fitted. A center electrode 3 having a protruding tip is fitted into the ceramic insulator 2. The center electrode 3 forms a discharge gap with the outer electrode 4 provided at the tip of the tubular metal shell 1.

Further, FIG. 2 is an enlarged cross-sectional view of a main part showing a cross section near the tip of the center electrode 3. The center electrode 3 has a thermocouple 5 (mainly a CA thermocouple) that is provided with an axial hole 31 extending from its rear portion to the vicinity of the tip thereof and forms a temperature sensor near the tip of the hole 31. The tip of the thermocouple 5 is the temperature measuring contact 5
1 and a pair of thermocouples 5, for example, chromel wire 52
And the connection point of the alumel line 53. At the rear end of the center electrode 3, a coaxial three-pole connecting terminal 6 including a pair of contacts 61, 62 for connecting the chromel wire 52 and the alumel wire 53 of the thermocouple 5 and a contact 63 for high voltage. Are formed.

An annular pressure sensor 7 is provided on the engine mounting seat surface of the tubular metal shell 1.
Is provided. The tubular metal shell 1 is composed of a hexagonal body 11, a large diameter body 12, a small diameter body 13 and a screw portion 14 in order from the upper side (rear end side) of FIG. The annular pressure sensor 7 is
It is brought into contact with the lower end surface of the large-diameter body portion 12, fitted onto the small-diameter body portion 13 and carried by the holding metal fitting 8 from below. Holding bracket 8
Is sealed by seam welding 9 to the outer periphery of the small-diameter body 13. FIG. 3 is an enlarged cross-sectional view of a main part surrounded by a circle C in FIG. 1, and the annular pressure sensor 7 used here is formed by laminating an annular piezoelectric element 71, an internal electrode 72, and an insulating plate 73, The inner and outer peripheries are sandwiched between insulators 74, the plate packing 75 is applied to the lower side, and the metal case 76 is incorporated. The upper and lower surfaces of the metal case 76 serve as pressure receiving plates,
Lead wire 77 is connected to. When the spark plug A is mounted on the head of the engine combustion chamber, the airtightness between the annular pressure sensor 7 and the tubular metal shell 1 is secured by the seam welding 9.

The annular pressure sensor 7 detects a change in pressure inside the combustion chamber and converts it into an electric signal.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view of a spark plug with a temperature and pressure sensor according to the present invention, FIG. 2 is an enlarged cross-sectional view of an essential part showing a cross section near the tip of its center electrode, and FIG. FIG. 4 is an enlarged cross-sectional view of the main part shown, and FIG. 4 is a cross-sectional view of a conventional spark plug with a temperature sensor. In the figure, 1 ... Cylindrical metal shell, 2 ... Ceramic insulator, 3
... Center electrode, 4 ... Outer electrode, 5 ... Thermocouple, 6 ... Coaxial type triode connection terminal, 7 ... Ring pressure sensor, 31 ... Hole, 61,6
2 ... Contactor, 63 ... High-voltage contactor, 71 ... Piezoelectric element,
72 ... Internal electrodes, 73 ... Insulation plate, 74 ... Insulator, 75 ...
Plate packing, 76 ... Metal case, 77 ... Lead wire, A ...
Spark plug with temperature and pressure sensor

Claims (2)

[Scope of utility model registration request] 1. A spark plug in which an insulator with a shaft hole is fitted in a tubular metal shell, and a center electrode is inserted into the shaft hole, wherein a hole in the axial direction from the rear part to the vicinity of the tip is bored in the center electrode, A temperature and a spark with a pressure sensor, in which a thermocouple is incorporated near the tip of the hole to form a temperature sensor for measuring the temperature of the tip of the center electrode, and an annular pressure sensor is arranged on the engine mounting seat surface of the metal shell. plug. 2. The coaxial three-pole connecting terminal comprising a contact for high voltage and a pair of contact for thermocouple is provided at the rear end of the center electrode. Spark plug with temperature and pressure sensor.